JPS6134928A - Growing process of element semiconductor single crystal thin film - Google Patents

Abstract

PURPOSE:To make it feasible to grow single crystal of element semiconductor subject to the precision of monomolecular layer on a substrate by a method wherein pressure inside a growing vessel, heating temperature of substrate and volume of introduced gas are specified. CONSTITUTION:A gate valve 2 is opened to vacuum a growing vessel 1 up to around 10<-7>-10<-8> Pa by an ultrahigh vacuum pump 3 and after heating an Si substrate 12 by a heater 10, one valve 6 is opened to introduce SiH2Cl2 8 for 0.5-10sec within the range boosting the pressure in the growing vessel 1 up to 10<-1>-10<-7> Pa. When, after closing the valve 6 to vacuum the gas inside the growing vessel 1, the other valve 2 is opened to introduce H2 9 for 2-200sec within the range boosting the pressure in the growing vessel 1 up to 10<-1>-10<-7> Pa, one monomolecular layer of Si is grown on the substrate 12. Then epitaxially grown layer of Si with specific thickness may be grown subject to the precision of molecular layer by means of repeating said procedures for growing monomolecular layers one after another.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for growing an elemental semiconductor single crystal thin film suitable for forming a single crystal growth layer of an elemental semiconductor on the order of a monomolecular layer.

[Prior art and its problems] Chemical vapor deposition (hereinafter referred to as CVD), molecular Line epitaxy method (hereinafter referred to as MBE method), atomic layer epitaxy method (hereinafter referred to as ALE method), etc. are known. However, in the CVD method, a Si compound as a source and hydrogen gas as a carrier are simultaneously introduced into a reaction chamber and grown by thermal decomposition, so the quality of the grown layer is poor. Further, there are drawbacks such as difficulty in controlling the monolayer order.

On the other hand, the MBE method, which is well known as a crystal growth method using an ultra-high vacuum, uses physical adsorption as the first step, so the quality of the crystal is inferior to the vapor phase growth method using a chemical reaction. Also,
Since the source itself is installed inside the growth chamber, it is difficult to control the gas released by heating the source and the amount of evaporation, and to replenish the source, making it difficult to maintain the growth rate constant for a long time. is difficult. In addition, the vacuum equipment, such as exhausting evaporated matter, becomes complicated. Furthermore, it is difficult to precisely control the stoichiometric composition (stoichiometry) of the compound semiconductor, and as a result, high quality crystals cannot be obtained.

In the MBE method, each semiconductor component element is vacuum-deposited at the same time, but the ALE method is an improved version of this method.
ntola et al. U, S, P, Nn4058430 (1
977), and M, Persa et al., J, voc, S
ci, Technol, A2. (1984), 41g
As announced on the page, the feature is that each constituent element of the compound is deposited alternately, and I-■, 1l-VI, and ■-
(2) Although it is a technique that is not suitable for growing thin films of compounds or oxides, it is an extension of the MBE method and cannot be expected to improve crystallinity. Furthermore, the ALE method is a technique suitable for growth on a glass substrate, and selective epitaxial growth, which is important in semiconductor integrated circuits, is difficult. Although attempts have been made to use ALE methods based on chemical reactions rather than ALE methods based on vapor deposition, polycrystals of 1l-Vl compounds such as ZnS or T
Compounds like a 202 are amorphous, and single crystal growth has not been successful. U, S, P,,
, Nα4058430, the ALE method uses the principle that a monoatomic layer of one element of a compound is bonded to a monoatomic layer of the other element, so it is a thin film growth method for compounds. Single-element semiconductors such as Sl and Ge cannot be grown by the ALE method. On the other hand, a paper by one of the inventors of the present application (Electronic Materials 1981 1
Although the February issue (page 19) mentions the possibility of applying the ALE method to a Si crystal growth method, it does not provide information on the specific growth temperature, amount of gas introduced, etc.

In this way, it is difficult to form high-quality crystals that satisfy the stoichiometric composition on the order of a monomolecular layer using the CVD method or the MBE method, whereas a single crystal cannot be obtained using the ALE method. The drawback was that it was impossible in principle to grow single-element semiconductors such as .

[Purpose of the Invention] The present invention provides a method for growing a single crystal thin film of an elemental semiconductor, which eliminates the drawbacks of the above-mentioned prior art, improves the quality of the crystal growth layer, and allows the growth film to be formed with the precision of a monomolecular layer. The purpose is to

[Summary of the Invention] Therefore, unlike the ALE method in which a single atomic layer of a single element is formed on a substrate, the present invention uses a gas containing molecules containing the component elements desired to be grown on the substrate from the outside. We investigated how to grow crystals on a substrate by introducing
As a result, the optimum values for the pressure inside the growth tank, the substrate heating temperature, and the amount of gas to be introduced were experimentally found, making it possible to grow a single crystal of an elemental semiconductor on the substrate.

[Embodiments of the invention] The present invention will be explained in detail below.

FIG. 1 shows a configuration diagram of an elemental semiconductor single crystal growth apparatus according to an embodiment of the present invention, in which 1 is a growth tank made of metal such as stainless steel, 2 is a gate valve, and 3 is inside the growth tank 1. 4 is a nozzle for introducing a gaseous compound of a component element of the group (■); 5 is a nozzle for introducing a gaseous compound that reacts with the nozzle 4; 6 and 7 are nozzles 4; , 5 is a valve that opens and closes, group 8 is a gaseous compound containing component elements, 9 is a gaseous compound that reacts with the gaseous compound 8, 10 is a heater for heating the substrate, and tungsten ( W) wire, and electric wires and the like are not shown. 11 is a thermocouple for temperature measurement, 12 is a semiconductor substrate, and 13 is a pressure gauge for measuring the degree of vacuum in the growth tank.

An example will be described in which a single crystal of Si is grown as a group (Ⅰ) element semiconductor with the above configuration. As a result of examining the crystal growth state using parameters such as the pressure inside the growth tank 1, the heating temperature of the substrate 12, and the amount of gas introduced, it was found that when the crystal is grown under the following conditions, a high quality single crystal thin film can be formed into a monomolecular layer. It was experimentally confirmed that it could be formed with precision. That is, in order to epitaxially grow a 5i single crystal layer by layer on the substrate 12, first open the gate valve 2 and turn on the ultra-high vacuum exhaust device 3.
The inside of the growth tank 1 is set to 10-7 to 10-” Pa5ca
1 (hereinafter abbreviated as Pa). Next, the Si substrate 12 is heated to 300 to 1100°C by the heater 10, and 5iH2CQ2 (dichlorosilane) 8 is added as a gas containing Sj to a pressure in the growth tank 1 of 10-1-10''.
The valve 6 is opened for 0.5 to 10 seconds and the water is introduced within the range of Pa. After that, after closing the valve 6 and exhausting the gas in the growth tank 1, the gas H29 that chemically reacts with 5i) 12c9z is pumped until the pressure in the growth tank 1 is 10-1 to 10'.
The valve 7 is opened for 2 to 200 seconds and the water is introduced within the range of Pa. As a result, one molecular layer of Si can be grown on the substrate 12. By repeating the above operations and growing monomolecular layers one after another, an epitaxial growth layer of Si having a desired thickness can be grown with the precision of a monomolecular layer. In addition, as a gas containing Si, SiCQ 4.5iHCQ
3.5ift 4 or a mixed gas of SiHa and Hl can be used.

FIG. 2 shows another embodiment of the present invention, which is for adding impurities. 14, 1.5 is a nozzle for introducing a gaseous compound used for adding impurities, 16.1
7 is a valve that opens and closes the nozzles 14 and 15; 18 is a gaseous compound containing a component element of group (1); and 19 is a gaseous compound containing a component element of group (2). Since the parts other than the addition of impurities are the same as the embodiment shown in FIG. 1, their explanation will be omitted.

When forming an n-type growth layer with this configuration, three gases, 5itlzCQz (dichlorosilane) 8 and Hl (hydrogen) 9 as introduced gases, and As1 (s (arsine) 18) as an impurity gas to be added, are introduced in a circulation manner. Another method is to introduce 5iH2CI228 and AsHs 18 at the same time and H2O alternately, or to introduce H2O and A, s
Impurities can be added by simultaneously introducing H318 and alternately with 5iH2CQ28. Alternatively, 5iH2CQ2 and AsH3 may be introduced alternately without introducing H2.

Furthermore, as another method, 5i) l 2 CΩ2 and H
2 and a first cycle of alternately introducing SiH2CΩ
By alternately repeating a second cycle in which As2 and AsH3 are simultaneously introduced alternately with H2, layers doped with As and undoped layers of As can be formed alternately and periodically. Furthermore, by adding a third cycle in which 5iH2CQ2 and PH3 (phosphine) are introduced at the same time and H2 is introduced alternately, A
A doped layer of s, with an atomic radius of 1" P
It is also possible to correct lattice distortion caused by the impurity atomic radius being different from the base semiconductor atomic radius by periodically forming a doped layer or a Si-only layer.

In addition, as the impurity addition gas source at this time,
AsCn3C (arsenic trichloride), PCQ3 (phosphorus trichloride), etc. can also be used.

Figure 3 shows Go and Si, which have a larger atomic radius than Si.
This figure shows an example in which B, which has an atomic radius smaller than that of B, is periodically doped at a constant ratio. As shown in FIG. 4(a), first, BCf13 and SiCΩ4 are introduced simultaneously, and then H2 is introduced. As a result, a monomolecular layer 51 doped with B is formed as shown in FIG. 5(b).

Next, by repeating twice the sequence of introducing 5iCQ4, evacuation, and introducing H2 in the sequence shown in the figure (a), two molecular layers of Si crystals are formed as shown in the figure (b). . Thereafter, in the same manner, after introducing BCQs and 5iCQa and evacuation, B-doped Si
Molecular layer formation. After introducing 5iCQ4 and evacuation, +(2 introduction operation is performed twice to form a bimolecular layer of Si.GeC
After introducing Qa and 5iCna and evacuation, a single molecular layer of Ge-doped Si is formed by introducing H2.

Next, the p-type growth layer was formed using B2H6 (diborane)19 as an impurity gas to be added.
28 and 829 in a circulating manner. Another method is to add impurities by simultaneously introducing 5iHxCR28 and B 2 H619 and alternately introducing H2O.

Incidentally, the impurity gases at this time are BCρ3, BBr
s, TMG (trimethyl gallium), TMII (trimethyl aluminum), T-MIn (trimethyl indium), etc. can also be used.

In this case, the flow rate of impurity gas introduced is 5iH2CQ28,
Compared to H2O, for example, 10 m' to 10. -' and the introduction time is set to 0.5 to 10 seconds, a molecular layer epitaxial growth layer having a desired impurity concentration distribution in the thickness direction can be formed. Also, by adjusting the amount and time of the impurity gas added.

ρn junction, non-uniform impurity density distribution, npn, npin
Of course, it is possible to realize bipolar transistor structures such as , pnp, and pnip, field effect transistors and static induction transistors such as n"in 10, n"nn 10, etc., and pnpn thyristor structures.

In each of the above embodiments, an example has been described in which the heating source for the substrate 12 is provided in the growth tank 1, but for example, as shown in FIG. 4, an infrared lamp 3 is used as the heating source.
The substrate 12 held on the susceptor 33 is heated using It may also be heated. In this way, members unnecessary for crystal growth can be removed from the inside of the growth tank 1, and generation of unnecessary gas components such as heavy metals due to heater heating can be prevented.

In addition, an optical system 4o is attached to the growth tank 1, and a mercury lamp, deuterium lamp, Xe lamp, excimer lamp, etc. are installed on the outside of the optical system 4o.
A light source 41 such as a laser or an Ar laser is provided, and a wavelength of 180
The substrate 12 may be irradiated with light of ~600 nm. In this case, the substrate temperature can be lowered, and as a result, a single crystal of even higher quality can be grown.

Incidentally, in the embodiments described above, a well-known ultra-high vacuum device such as an ion pump can be used. Furthermore, it goes without saying that an auxiliary vacuum chamber for loading and unloading the single crystal substrate, a crystal drawing device, etc. can be easily added, and the device can be easily mass-produced. Furthermore, although the gas used for crystal growth has mainly been described with respect to Si, it is of course applicable to other group III semiconductors such as Ge.

Furthermore, the substrate is not limited to Sl, but may be made of sapphire, spinel, or the like.

[Effects of the Invention] As described above, according to the present invention, a single crystal of a high-quality elemental semiconductor can be formed layer by layer on a substrate. Also,
Since impurities can be added layer by layer while taking into account the correction of the lattice distortion of the base semiconductor single crystal by introducing impurities, it is possible to obtain a very steep impurity density distribution while maintaining good crystallinity. very fast transistors,
It exhibits excellent effects in the production of integrated circuits, diodes, optical elements, etc.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are block diagrams of crystal growth apparatuses according to each embodiment of the present invention, and FIG. 3 is an explanatory diagram of doping Si with Ge and B, and (a) shows a gas introduction pulse. (b) is a schematic diagram of a growth layer doped with Ge and B, and FIG. 4 is a configuration diagram of a crystal growth apparatus according to yet another embodiment of the present invention. 1... Growth tank, 2... Gate valve, 3... Exhaust device, 4, 5, 14. 15... Nozzle, 6, 7, 16
．． 17... Valve, 8,9,18.19... Gaseous compound, 10 - Heater, 11... Thermocouple,
12... Board, 13... Pressure gauge.・-',\ Agent Patent attorney Crest 1) Makoto 1□)-'-/' Figure 7 Figure 2

Claims (13)

[Claims] (1) Gaseous molecules containing component elements of an elemental semiconductor are grown at a pressure within the growth tank of 1 to 10^-^6 Pascals.
The gaseous molecules that chemically react with the gas molecules are introduced onto the substrate for 5 to 200 seconds, and after being evacuated, the pressure inside the growth tank is 1 to 1.
A series of operations of introducing and evacuation onto the substrate for 0.5 to 200 seconds in the range of 10^-^6 Pascals to a substrate temperature of 3
1. A method for growing an elemental semiconductor single crystal thin film, which comprises growing a single crystal thin film of an elemental semiconductor to a desired thickness with the precision of a monomolecular layer by repeating the heating at 00 to 1100°C. (2) In claim 1, the gaseous molecules containing impurity elements of the elemental semiconductor react with the gaseous molecules containing the component elements of the elemental semiconductor or the gas containing the component elements of the elemental semiconductor. A method for growing an elemental semiconductor single crystal thin film having a desired impurity concentration distribution in the thickness direction with monomolecular layer precision by introducing simultaneously or alternately with one of the molecules. (3) In claim 1, gaseous molecules react periodically with a gas containing a component element of the elemental semiconductor or a gas containing a component element of the elemental semiconductor during repetition of the operation. A method for growing an elemental semiconductor single crystal thin film, in which a molecular layer containing an impurity element and a molecular layer not containing an impurity element are periodically formed by flowing molecules containing an impurity element of the elemental semiconductor at the same time as any of the above. (4) Growth of an elemental semiconductor single crystal thin film according to claim 2 or 3, in which gaseous molecules containing at least two or more types of impurity elements of the elemental semiconductor are periodically introduced. Law. (5) In claim 4, gaseous molecules containing at least two or more types of impurity elements are introduced in different cycles or at different times for each type. A method for growing single-crystal thin films of elemental semiconductors in which different types of impurity elements are periodically included in different molecular layers. (6) In the statement of either claim 4 or 5, at least one of the at least two types of impurity elements has an atomic radius larger than the atomic radius of the elemental semiconductor, and the remaining impurities A method for growing an elemental semiconductor single crystal thin film in which the atomic radius of at least one of the elements is smaller than the atoms of the elemental semiconductor. (7) In any one of claims 4, 5, and 6, at least one of the impurity elements is
A method for growing single crystal thin films of elemental semiconductors, which are group IV elements. (8) A method for growing an elemental semiconductor single crystal thin film according to any one of claims 4, 5, and 6, in which the impurity elements are of the same conductivity type. (9) A method for growing an elemental semiconductor single crystal thin film according to any one of claims 1 to 8, wherein the elemental semiconductor is Si. (10) In any one of claims 1 to 8, the gaseous molecule containing the component element of the semiconductor is any one of SiH_2Cl_2, SiHCl_3, and SiCl_4, and the gaseous molecule and the chemical A method for growing single crystal thin films of elemental semiconductors in which the reacting gaseous molecules are hydrogen molecules. (11) A method for growing an elemental semiconductor single crystal thin film according to any one of claims 1 to 8, characterized in that the substrate is irradiated with light. (12) A method for growing an elemental semiconductor single crystal thin film according to any one of claims 1 to 8, characterized in that the substrate is irradiated with light of at least two different wavelengths. (13) A method for growing an elemental semiconductor single crystal thin film according to claim 5, characterized in that light of different wavelengths is irradiated when introducing the different impurity elements.